Intercropping

Intercropping is the practice of growing two or more crops together in the same field. Intercropping may provide benefits such as increased yield or decreased pest infestations. Historically, peasant farmers around the world have intercropped. However, since the advent of industrialized agriculture, intercropping has often been abandoned in favor of monoculture.

Measuring Intercropped Yields
Crop yields in intercropped fields can be measured using the Land Equivalent Ratio (LER), "the ratio of the area under sole cropping to the area under intercropping needed to give equal amounts of yield at the same management level. It is the sum of the fractions of the intercropped yields divided by the sole-crop yields." In other words, if one acre of monoculture can produce 150 bushels of corn or 40 bushels of beans, but one acre of intercropped corn and beans produces 90 bushels of corn and 30 bushels of beans, then the LER is calculated as (90/150) + (30/40) = 1.35. Therefore, one acre of intercropped corn and beans produces as much yield as 1.35 acres of monoculture split between corn and beans. Scientists test various crop combinations to calculate their LER in order to determine which crops are the most productive when intercropped.

A common mistake involves judging crop yields for intercropped fields without calculating LER. When one does that, it can appear that crop yields actually decrease with intercropping, not increase. In the example above, a farmer obtained the equivalent of 1.35 acres of corn and beans from one intercropped field. However, if one solely compares an acre of corn alone with an acre of corn intercropped with beans, they may say that 90 bushels of corn (in the intercropped example) is less than 150 bushels of corn grown alone, and therefore intercropping decreases yield. This is inaccurate.

Intercropping in Mexican Milpas
One of the most famous intercropped combinations is corn, beans, and squash, which are planted together in Mexican cornfields, known as milpas. During the Green Revolution, agronomists encouraged farmers to abandon intercropping in favor of monocultures, but peasant farmers, by and large, continued to practice intercropping.


 * "Mangelsdorf knew that many campesinos intercropped corn and beans, and the MAP's scientists too this "ancient custom" into account when they began working on beans, believing that "it was likely to persist for generations to come," but they also said that it lowered yield of both crops. Bean research targeted commercial growers who monocropped and used insecticides. The MAP did not create seeds to solve the problems of peasant farmers."

Related Sourcewatch articles

 * Rockefeller Foundation
 * Mexican Agricultural Program
 * Green Revolution